1. Field of the Invention
The present invention relates to a new therapeutic use of ergoline derivatives having the formula I ##STR2## wherein R.sub.1 represents a hydrogen atom or methyl group, either R.sub.2 and R.sub.3 represent hydrogen atoms or together represent a chemical bond, R.sub.4 represents a hydrogen atom or a C.sub.1 -C.sub.4 alkyl group, R.sub.5 represents a C.sub.1 -C.sub.4 alkyl group or an allyl group and R.sub.6 represents a hydrogen or hologen atom; and pharmaceutically acceptable salts thereof.
2. Description of the Background
The compounds of the formula I and their preparation are described in U.S. Pat. No. 4,728,649, which is hereby incorporated by reference. This shows their functional anti-dopaminergic activity in normal mice. The compounds are said to have moderate to good anti-hypertensive activity and to be useful as anxiolytic and antipsychotic agents.
It is known that bromocriptine, an ergot derivative with dopaminergic activity, is an effective antiparkinson agent, but severe side effects limit the clinical usefulness of this drug. Adverse effects of bromocriptine include emesis, hypotension, cardiac arrhythmia, digital vasospasm in cold weather, conjunctival irritation, diplopia, nasal stuffiness, constipation and syndrome of bilateral red, tender edema of the lower limbs and neuroendocrine alterations. These problems are due to the fact that bromcriptine exerts its agonist effect on both central and peripheral populations of dopamine receptors.
There continues to remain a need for new and more effective antiparkison agents, which do not possess the drawbacks of the prior art compounds.